/*
 * Bytecode Analysis Framework
 * Copyright (C) 2003-2007 University of Maryland
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

package edu.umd.cs.findbugs.ba;

import java.io.Serializable;
import java.util.Comparator;
import java.util.Iterator;
import java.util.TreeSet;

import org.apache.bcel.generic.InstructionHandle;
import org.apache.bcel.generic.MethodGen;

import edu.umd.cs.findbugs.SystemProperties;
import edu.umd.cs.findbugs.ba.deref.UnconditionalValueDerefAnalysis;
import edu.umd.cs.findbugs.ba.deref.UnconditionalValueDerefDataflow;
import edu.umd.cs.findbugs.ba.deref.UnconditionalValueDerefSet;
import edu.umd.cs.findbugs.classfile.CheckedAnalysisException;
import edu.umd.cs.findbugs.classfile.DescriptorFactory;
import edu.umd.cs.findbugs.classfile.Global;

/**
 * Perform dataflow analysis on a method using a control flow graph.
 * Both forward and backward analyses can be performed.
 * <ul>
 * <li> The "start" point of each block is the entry (forward analyses)
 * or the exit (backward analyses).
 * <li> The "result" point of each block is the exit (forward analyses)
 * or the entry (backward analyses).
 * </ul>
 * The analysis's transfer function is applied to transform
 * the meet of the results of the block's logical predecessors
 * (the block's start facts) into the block's result facts.
 *
 * @author David Hovemeyer
 * @see CFG
 * @see DataflowAnalysis
 */
public class Dataflow <Fact, AnalysisType extends DataflowAnalysis<Fact>> {
	private CFG cfg;
	private AnalysisType analysis;
	private BlockOrder blockOrder;
	private boolean isForwards;
	private int numIterations;

	public static boolean DEBUG = SystemProperties.getBoolean("dataflow.debug");

	/**
	 * Constructor.
	 *
	 * @param cfg      the control flow graph
	 * @param analysis the DataflowAnalysis to be run
	 */
	public Dataflow(CFG cfg, AnalysisType analysis) {
		this.cfg = cfg;
		this.analysis = analysis;
		blockOrder = analysis.getBlockOrder(cfg);
		isForwards = analysis.isForwards();
		numIterations = 0;

		// Initialize result facts
		Iterator<BasicBlock> i = cfg.blockIterator();
		while (i.hasNext()) {
			BasicBlock block = i.next();

			Fact result = analysis.getResultFact(block);
			if (block == logicalEntryBlock()) {
				try {
					// Entry block: set to entry fact
					analysis.initEntryFact(result);
				} catch (DataflowAnalysisException e) {
					analysis.makeFactTop(result);
				}
			} else {
				// Set to top
				analysis.makeFactTop(result);
			}
		}
	}

	// Maximum number of iterations before we assume there is a bug and give up.
	private static final int MAX_ITERS = SystemProperties.getInt("dataflow.maxiters", 97);

	private String getFullyQualifiedMethodName() {
		String methodName;
		MethodGen methodGen = cfg.getMethodGen();
		if (methodGen == null)
			methodName = cfg.getMethodName();
		else methodName = SignatureConverter.convertMethodSignature(methodGen);
		return methodName;
	}
	static class ForwardProgramOrder implements Comparator<BasicBlock>, Serializable  {

        public int compare(BasicBlock o1, BasicBlock o2) {
        	int p1 = o1.getLabel();
			int p2 = o2.getLabel();
        	return p1 - p2;
        }
		
	}
	static class BackwardProgramOrder extends  ForwardProgramOrder {

		@Override
        public int compare(BasicBlock o1, BasicBlock o2) {
        	return - super.compare(o1, o2);
        }
		
	}
	/**
	 * Run the algorithm.
	 * Afterwards, caller can use the getStartFact() and getResultFact() methods to
	 * to get dataflow facts at start and result points of each block.
	 */
	public void execute() throws DataflowAnalysisException {
		boolean change;
		boolean debugWas = DEBUG;
		if (DEBUG) {
			reportAnalysis("Executing");
		}

		int timestamp = 0;
		boolean firstTime = true;
		do {
			change = false;
			++numIterations;
			if (numIterations > MAX_ITERS && !DEBUG ) {
				DEBUG = true;
				reportAnalysis("Too many iterations");
				System.out.println(this.getClass().getName());
				if (this.getClass() == UnconditionalValueDerefDataflow.class || this.getClass() == LiveLocalStoreDataflow.class) {
					try {
	                    ClassContext cc = Global.getAnalysisCache().getClassAnalysis( ClassContext.class, DescriptorFactory.createClassDescriptorFromDottedClassName(cfg.getMethodGen().getClassName()));
	                    System.out.println("Forwards cfg");
	                    CFGPrinter printer = new CFGPrinter(cfg);
	                    printer.setIsForwards(true);
	                    printer.print(System.out);
	                    System.out.println("Backwards cfg");
	                    printer = new CFGPrinter(cfg);
	                    printer.setIsForwards(false);
	                    printer.print(System.out);
	                    cc.dumpSimpleDataflowInformation(cfg.getMethodGen().getMethod());
					} catch (CheckedAnalysisException e) {
	                   e.printStackTrace(System.out);
                    }
				}
			}

			
			if (DEBUG) {
				System.out.println("----------------------------------------------------------------------");
				System.out.println(this.getClass().getName() + " iteration: " + numIterations + ", timestamp: " + timestamp);
				MethodGen mg = cfg.getMethodGen();
				System.out.println(mg.getClassName()+"." +mg.getName() + mg.getSignature());
				System.out.println("----------------------------------------------------------------------");
		
			}

			if (numIterations >= MAX_ITERS+9) {
				throw new AssertionError( "Too many iterations (" + numIterations + ") in dataflow when analyzing " + getFullyQualifiedMethodName());
			}

			analysis.startIteration();
			
			if (DEBUG && firstTime && blockOrder instanceof ReverseDFSOrder) {
					ReverseDFSOrder rBlockOrder = (ReverseDFSOrder) blockOrder;
					System.out.println("Entry point is: " + logicalEntryBlock());
					System.out.println("Basic block order: ");
					Iterator<BasicBlock> i = blockOrder.blockIterator();
					while (i.hasNext()) {

						BasicBlock block = i.next();
						debug(block, "rBlockOrder " + rBlockOrder.rdfs.getDiscoveryTime(block) + "\n");
				}
			}
			Iterator<BasicBlock> i = blockOrder.blockIterator();
			if (numIterations > 3 && numIterations %2 == 0 && blockOrder instanceof ReverseDFSOrder) {
				if (DEBUG) System.out.println("Trying program order");
				TreeSet<BasicBlock> bb = new TreeSet<BasicBlock>(new BackwardProgramOrder());
				Iterator<BasicBlock> j = blockOrder.blockIterator();
				while (j.hasNext()) {
					BasicBlock block = j.next();
					bb.add(block);
				}
				if (DEBUG) for(BasicBlock block : bb) {
					debug(block, "\n");
				}
				i = bb.iterator();
			}
			if (DEBUG) 
				dumpDataflow(analysis);
				


			// For each block in CFG...

			while (i.hasNext()) {

				BasicBlock block = i.next();
				
				// Get start fact for block.
				Fact start = analysis.getStartFact(block);
				assert start != null;
				
				boolean needToRecompute = false;
				//				 Get result facts for block,
				Fact result = analysis.getResultFact(block);
				assert result != null;
				
				int originalResultTimestamp = analysis.getLastUpdateTimestamp(result);

				// Meet all of the logical predecessor results into this block's start.
				// Special case: if the block is the logical entry, then it gets
				// the special "entry fact".
				if (block == logicalEntryBlock()) {
					analysis.makeFactTop(start);
					analysis.initEntryFact(start);
					if (DEBUG) debug(block, "Init entry fact ==> " + analysis.factToString(start) + "\n");
					needToRecompute = true;
				} else {
					int lastCalculated = analysis.getLastUpdateTimestamp(start);
					Iterator<Edge> predEdgeIter = logicalPredecessorEdgeIterator(block);

					int predCount = 0;
					int rawPredCount = 0;
					while (predEdgeIter.hasNext()) {
						Edge edge = predEdgeIter.next();
						rawPredCount++;
						if (needToRecompute) continue;
						BasicBlock logicalPred = isForwards ? edge.getSource() : edge.getTarget();

						// Get the predecessor result fact
						Fact predFact = analysis.getResultFact(logicalPred);
						int predLastUpdated = analysis.getLastUpdateTimestamp(predFact);
						if (!analysis.isTop(predFact)) {
							predCount++;
							if (predLastUpdated >= lastCalculated) {

								needToRecompute = true;
								if (DEBUG) {
									debug(block, "\n Need to recompute. My timestamp = " + lastCalculated + ", pred timestamp = " + predLastUpdated + ",\n   pred fact = " + predFact +"\n");
								}
							    // break;
							}
						}
					}
					if (predCount == 0) needToRecompute = true;

					if (!needToRecompute) {
						continue;
					}

					if (needToRecompute) {

						analysis.makeFactTop(start);
						predEdgeIter = logicalPredecessorEdgeIterator(block);
						while (predEdgeIter.hasNext()) {
							Edge edge = predEdgeIter.next();
							BasicBlock logicalPred = isForwards ? edge.getSource() : edge.getTarget();

							// Get the predecessor result fact
							Fact predFact = analysis.getResultFact(logicalPred);

							// Apply the edge transfer function.
							Fact edgeFact = analysis.createFact(); 
							analysis.copy(predFact, edgeFact);
							analysis.edgeTransfer(edge, edgeFact);

							if (DEBUG && !analysis.same(edgeFact, predFact)) {
								debug(block, logicalPred, edge,
										"Edge transfer " + analysis.factToString(predFact) + " ==> " + analysis.factToString(edgeFact));
							}

							// Merge the predecessor fact (possibly transformed by the edge transfer function)
							// into the block's start fact.
							if (DEBUG) {
								if (analysis.isTop(start))
									debug(block, logicalPred, edge, "\n  First pred is " + analysis.factToString(edgeFact)  + "\n   last updated at " +  analysis.getLastUpdateTimestamp(predFact) +"\n");
								else
								debug(block, logicalPred, edge, "\n  Meet " + analysis.factToString(start) + "\n   with " + analysis.factToString(edgeFact) 

									+ "\n   pred last updated at " +  analysis.getLastUpdateTimestamp(predFact) +"\n");
							}


							if (analysis instanceof UnconditionalValueDerefAnalysis) {
								((UnconditionalValueDerefAnalysis)analysis).meetInto((UnconditionalValueDerefSet)edgeFact, edge, (UnconditionalValueDerefSet) start, rawPredCount==1);
							}
							else analysis.meetInto(edgeFact, edge, start);
							analysis.setLastUpdateTimestamp(start, timestamp);

							int pos = -1;
							if (block.getFirstInstruction() != null)
								pos = block.getFirstInstruction().getPosition();
							if (DEBUG) System.out.println(" [" + pos +"]==> " + analysis.factToString(start) +" @ " + timestamp + " \n");
						}
					}
				}
				if (DEBUG) debug(block, "start fact is " + analysis.factToString(start) + "\n");

				// making a copy of result facts (so we can detect if it changed).
				boolean resultWasTop = analysis.isTop(result);
				Fact origResult = null;
				if (!resultWasTop) {
					origResult = analysis.createFact();
					analysis.copy(result, origResult);
				}

				if (true || analysis.isTop(start)) {
					// Apply the transfer function.

					analysis.transfer(block, null, start, result);
				} else {
					analysis.copy(start, result);
				}

				if (DEBUG && SystemProperties.getBoolean("dataflow.blockdebug")) {
					debug(block, "Dumping flow values for block:\n");
					Iterator<org.apache.bcel.generic.InstructionHandle> ii = block.instructionIterator();
					while (ii.hasNext()) {
						org.apache.bcel.generic.InstructionHandle handle = ii.next();
						Fact tmpResult = analysis.createFact();
						analysis.transfer(block, handle, start, tmpResult);
						System.out.println("\t" + handle + " " + analysis.factToString(tmpResult) );
					}
				}

				// See if the result changed.
				if (DEBUG) debug(block, "orig result is " + (origResult == null ? "TOP" : analysis.factToString(origResult) ) + "\n");
				boolean thisResultChanged = false;
				if (resultWasTop)
					thisResultChanged = !analysis.isTop(result);
				else thisResultChanged = !analysis.same(result, origResult);
				if (thisResultChanged) {
					timestamp++;
					if (DEBUG) debug(block, "result changed at timestamp " + timestamp + "\n");
					if (DEBUG && !needToRecompute) {
						System.out.println("I thought I didn't need to recompute");
					}
					change = true;
					analysis.setLastUpdateTimestamp(result, timestamp);
				} else
					analysis.setLastUpdateTimestamp(result, originalResultTimestamp);

				if (DEBUG) debug(block, "result is " + analysis.factToString(result) + " @ timestamp " 
						+ analysis.getLastUpdateTimestamp(result) + "\n");
			}

			analysis.finishIteration();
		} while (change);
		
		if (DEBUG) {
				System.out.println("-- Quiescence achieved-------------------------------------------------");
				System.out.println(this.getClass().getName() + " iteration: " + numIterations + ", timestamp: " + timestamp);
				MethodGen mg = cfg.getMethodGen();
				System.out.println(mg.getClassName()+"." +mg.getName() + mg.getSignature());
				new RuntimeException("Quiescence achieved----------------------------------------------------------------").printStackTrace(System.out);

		}
		DEBUG = debugWas;
	}
	/**
	 * @param msg TODO
     * 
     */
    private void reportAnalysis(String msg) {
	    String shortAnalysisName = analysis.getClass().getName();
	    int pkgEnd = shortAnalysisName.lastIndexOf('.');
	    if (pkgEnd >= 0) {
	    	shortAnalysisName = shortAnalysisName.substring(pkgEnd + 1);
	    }
	    System.out.println(msg + " " + shortAnalysisName + " on " + getFullyQualifiedMethodName());
    }

	private static String blockId(BasicBlock bb) {
		InstructionHandle handle = bb.getFirstInstruction();
		if (handle == null) return ""+ bb.getLabel();
		return bb.getLabel()+":"+ handle.getPosition() + " " + handle.getInstruction();
	}
	private static void debug(BasicBlock bb, String msg) {


		System.out.print("Dataflow (block " + blockId(bb) + "): " + msg);
	}

	private static void debug(BasicBlock bb, BasicBlock pred, Edge edge, String msg) {
		System.out.print("Dataflow (block " + blockId(bb) + ", predecessor " + blockId(pred) +
				" [" + Edge.edgeTypeToString(edge.getType()) + "]): " + msg);
	}

	/**
	 * Return the number of iterations of the main execution loop.
	 */
	public int getNumIterations() {
		return numIterations;
	}

	/**
	 * Get dataflow facts for start of given block.
	 */
	public Fact getStartFact(BasicBlock block) {
		return analysis.getStartFact(block);
	}

	/**
	 * Get dataflow facts for end of given block.
	 */
	public Fact getResultFact(BasicBlock block) {
		return analysis.getResultFact(block);
	}
	
	/**
	 * Get dataflow fact at (just before) given Location.
	 * Note "before" is meant in the logical sense, so for backward analyses,
	 * before means after the location in the control flow sense.
	 * 
	 * @param location the Location
	 * @return the dataflow value at given Location
	 * @throws DataflowAnalysisException
	 */
	public /*final*/ Fact getFactAtLocation(Location location) throws DataflowAnalysisException {
		return analysis.getFactAtLocation(location);
	}
	
	/**
	 * Get the dataflow fact representing the point just after given Location.
	 * Note "after" is meant in the logical sense, so for backward analyses,
	 * after means before the location in the control flow sense.
	 * 
	 * @param location the Location
	 * @return the dataflow value after given Location
	 * @throws DataflowAnalysisException
	 */
	public /*final*/ Fact getFactAfterLocation(Location location) throws DataflowAnalysisException {
		return analysis.getFactAfterLocation(location);
	}
	
	/**
	 * Get the fact that is true on the given control edge.
	 * 
	 * @param edge the edge
	 * @return the fact that is true on the edge
	 * @throws DataflowAnalysisException 
	 */
	public Fact getFactOnEdge(Edge edge) throws DataflowAnalysisException {
		return analysis.getFactOnEdge(edge);
	}

	/**
	 * Get the analysis object.
	 */
	public AnalysisType getAnalysis() {
		return analysis;
	}

	/**
	 * Get the CFG object.
	 */
	public CFG getCFG() {
		return cfg;
	}

	/**
	 * Return an Iterator over edges that connect given block to its
	 * logical predecessors.  For forward analyses, this is the incoming edges.
	 * For backward analyses, this is the outgoing edges.
	 */
	private Iterator<Edge> logicalPredecessorEdgeIterator(BasicBlock block) {
		return isForwards ? cfg.incomingEdgeIterator(block) : cfg.outgoingEdgeIterator(block);
	}

	/**
	 * Get the "logical" entry block of the CFG.
	 * For forward analyses, this is the entry block.
	 * For backward analyses, this is the exit block.
	 */
	private BasicBlock logicalEntryBlock() {
		return isForwards ? cfg.getEntry() : cfg.getExit();
	}
	
	
	public void dumpDataflow(AnalysisType analysis) {
		System.out.println(this.getClass().getName() + " analysis for " + getCFG().getMethodName() + getCFG().getMethodSig() + " { ");
    	try {
    		
    	for(Location loc : getCFG().orderedLocations()) {
    		System.out.println("\nBefore: " + analysis.factToString(getFactAtLocation(loc)));
    		System.out.println("Location: " + loc);
    		System.out.println("After: " + analysis.factToString(getFactAfterLocation(loc)));	
    	}
    	} catch (DataflowAnalysisException e) {
    		AnalysisContext.logError("error dumping dataflow analysis", e);
    		System.out.println(e);
    	}
    	System.out.println("}");
    }
}

// vim:ts=4
